The present invention relates, in general, to optical devices and, more particularly, to package assemblies for optical transmitters.
Laser diodes are used in a wide range of electronic applications including compact disk players and drives, bar code readers, and other similar identification and data storage technologies. These laser diodes are typically side-emitting lasers that are mounted in special metal cans having a clear lens in the top of the can. There are several industry standard metal cans for these applications, for example the well-known TO-18, 46, and 56 metal cans.
Because side-emitting lasers generate significant heat and degrade if overheated, it is necessary to use metal cans like the above to provide sufficient heat dissipation during operation. Typically, the metal can is mounted to a header, a laser die is mounted on a post that rises vertically above the header, and a lens is mounted separately on top of the metal can. The resulting package is often not hermetic.
The above metal can packages suffer from several disadvantages including high manufacturing costs due to the need for a special mounting header and metal can. Further, side-emitting lasers cannot be tested prior to singulation from a semiconductor wafer. Therefore, manufacturing yields are depressed. Moreover, with this prior metal can package, critical optical alignment of the laser diode and the package is required at the time of manufacturing an optical end product, at which time the metal can package must be mated to another optical component, such as an optical tube containing lenses. Alignment at this point in manufacture is critical because tolerances are as small as 10 microns. As a result of this critical alignment and tight tolerance, yield losses are significant. Accordingly, there is a need for an improved laser diode package assembly that has reduced manufacturing cost, improved yields, and that does not require critical alignment at a late point in the manufacture of an optical application end product.